Immunodecoration of proteins containing Tyr-P on electroblots is possible by incubating the electroblot of SDS gels with sheep antibodies which bind Tyr-P. The region of the blot with bound antibodies is detected with affinity purified anti sheep IgG conjugated with horseradish peroxidase. The procedure was tested with authentic proteins containing Tyr-P or Ser-P residues and appears to be specific. This has been used to identify calpactin in lens protein extracts and protein substrates of several growth factor receptor tyrosine kinases. Immunoadsorption of phosphotyrosyl proteins (PTP) has been accomplished by immobilization of anti-phosphotyrosine (a-YP) antibodies to protein-A Sepharose or covalent linkage by CNBr activated Sepharose. These preparations allow semiquantitative absorption of tyrosine phosphorylated epidermal growth factor receptor and the insulin receptor.